The present invention relates to an Al—Mg—Si aluminum alloy extruded product that exhibits high fatigue strength, excellent impact fracture resistance, and excellent formability.
In recent years, automotive components made of aluminum have been studied and used in practice in order to reduce the weight of automobiles to improve travel performance and reduce fuel consumption from the viewpoint of environment protection.
Since an aluminum alloy structural material used for automobiles or the like is repeatedly subjected to impact during travel, it is necessary to design the material taking account of the fatigue strength of the material.
Therefore, a high-strength material is used to provide fatigue strength. A component that is directly subjected to and absorbs impact during travel is also required to exhibit high impact fracture resistance.
However, high-strength aluminum alloys that have been proposed exhibit poor extrusion productivity so that the production cost increases.
When producing an aluminum structural material used for automotive underbody parts or the like, the product may require press working or bending depending on the shape of the product. When using a high-strength material, cracks or orange peeling occur on the surface of the material during press working or bending. The fatigue strength of the material decreases due to such surface defects. Therefore, the surface defects must be removed by a mechanical polishing step (e.g., buffing) so that the production cost increases.
JP-A-2005-82816 discloses an aluminum alloy forged material that exhibits high-temperature fatigue strength. However, the Al—Cu aluminum alloy disclosed in JP-A-2005-82816 is suitable for a forged material, but cannot be applied to an extruded product.
An object of several aspects of the invention is to provide an Al—Mg—Si aluminum alloy extruded product that exhibits high extrusion productivity, high fatigue strength, excellent impact fracture resistance, and excellent formability.